The present invention introduces a fire suppression system for transportation tunnels and mines and methods of selective delivery of breathable fire-suppressive composition directly to the location affected by fire. The invented system is mostly suitable for installation in existing automobile and railroad tunnels without interruption of traffic. The system is also suited to provide complete fire safety in mines and other underground facilities, multilevel parking garages, industrial complexes, office and apartment buildings, schools, hospitals, shopping and entertainment centers and other enclosed compartments and environments.
This invention is an important addition and improvement of the Fire Prevention and Suppression Systems (FirePASS(trademark)) described in earlier patent applications provided above.
Tunnel fires have been usually divided into three types based on their order-of-magnitude rate of energy output. They are: small automobile fires (1 MW); medium fires (10 MW); and major and catastrophic fires (100 MW and higher). Small automobile fires are routine incidents, occurring as frequently as weekly in congested urban tunnels. Such reported fires have been universally extinguished without difficulty to date.
However, the catastrophic fire following a suicidal terrorist attack in a congested traffic tunnel remains to be the most critical scenario, for which emergency services and authorities are unequipped and unprepared. It is relatively uncomplicated to organize and carry out such attack. For instance a regular track can be used, loaded with flammable liquid canisters or pressurized propane gas containers. Such an attack can cause a significant initial structural damage with a consequent catastrophic fire and numerous fatalities.
Devastating tunnel fires demonstrate that their consequences depend entirely on the tunnel ventilation. Due to the necessity of providing adequate ventilation, a fire in a queue in an urban tunnel with a mixed fire load of passenger cars, buses and trucks could easily develop into catastrophe. Fire services will not be able to tackle these fires until it is too late, because radiant heat and smoke production is too great. This was the case in the last tunnel fire (October 2001, St-Gotthard tunnel), when firefighters could not even enter the tunnel until combustible materials were consumed by fire. Enhanced ventilation can also develop as a result of the chimney effect, as in the London Subway Fire and in the Kaprun disaster.
Current fire-preventative and fire-suppressive methods are totally insufficient in dealing with catastrophic tunnel fires. Several systems, either installed or contemplatedxe2x80x94aside from their effectiveness during normal operationsxe2x80x94show little capability of satisfactory operation during a catastrophic fire emergency. These are fire extinguishers, stand pipes, and sprinklers (including water mist sprinklers) with their ancillary systems of water supply and drainage, and different types of ventilation. The standard safety-supporting systems (communication, ventilation, lighting, and escape), primarily support the comfort and well-being of persons in a tunnel during normal operations, but their functions during catastrophic events are insufficient, as was revealed in the Channel Tunnel fire in 1996.
Automatic fire suppression systems based on water mist may be of little benefit in preventing structural damage to a tunnel and will not be effective in reducing loss of life in the event of a terrorist act followed by a catastrophic tunnel fire. The fire will probably be fully developed before the suppression system would be activated. The explosion can damage the water pipe system before it can create sufficient pressure for sprinklers. There will be a time lag between fire ignition and the activation of the water suppression system, which, in cold climates, must be initially dry. It will take time until pumps are started, valves are opened, and the delivery system piping is filled with water. Vehicular tunnel conditions cannot exploit sprinkler or water mist system strengths and turn most of them to a disadvantage. Tunnels are very long and narrow, often sloped laterally and longitudinally, vigorously ventilated, and never subdivided, so heat will normally not be localized over a fire. A catastrophic, hazardous-material fire will grow and spread hot combustion products far from its origin before sprinkler heads open, especially in colder regions where the water-suppression system is by necessity a dry one.
An inordinately large flow of water would be required to deliver an effective spray through all the potentially-open heads to assure application upon the fire itself. Besides that, since the fires usually originate from the lower part of a vehicle there will be no efficient fire suppression from sprinklers placed on the ceiling or walls of a tunnel.
Automatic activation of the sprinklers by active detectors would of necessity be delayed until all traffic could be halted, since even light spray would catch drivers unaware, and would dangerously slicken the roadway. Water squirting from the ceiling of a subaqueous tunnel would suggest tunnel failure and induce panic in motorists. Inadvertent activation is clearly unacceptable. Moreover, discharging water onto a fully developed catastrophic fire within an enclosed tunnel may only increase the danger to the tunnel occupants because of the steam generated when water contacts the fire.
Available publications and statistical data clearly indicate that currently no adequate and reliable fire-preventative and fire-suppressing technology for traffic tunnels is available anywhere in the world.
The new fire-safety technology, FirePASS(trademark) (Fire Prevention And Suppression System), recently developed by the inventor and described in previous patent applications provided above, can help resolve the complex problem of fire safety in transportation tunnels, as well as in normally occupied facilities in general. FirePASS(trademark) can minimize structural damage and fatalities in terrorist attacks. This system is effective in the prevention and instant extinguishing of fire of any possible origin and size. It is also absolutely safe for people and is user-friendly, while completely excluding any damage of equipment and property.
The system can be referred as related to Total Flood Clean Agent Systems, but it has significant differences from them. The FirePASS(trademark) works by creating a safe human-breathable atmosphere in which nothing can be ignited or burn. This technology employs the Normobaric Breathable Hypoxic Air (NBHA) for prevention and suppression of fire.
FirePASS technology for tunnels is based on two properties that differentiate it from all other total flood clean agent systems:
1. The hypoxic generator produces oxygen-reduced air with a preset fire-suppressive, but safe for human breathing, concentration of oxygen. This eliminates the necessity of oxygen monitoring to control the tunnel atmosphere within the range of preset parameters. It also eliminates the complicated and vulnerable electronic feedback circuits that are sensible to structural and fire-related damage.
2. When in use, the protected space is constantly ventilated with fire-suppressive, breathable hypoxic air. This creates normal or even improved hygienic conditions for occupants of the tunnel while the hypoxic generator produces HEPA-filtered, normal-humidity air. Constant ventilation allows the prompt evacuation of toxic combustion gases without feeding fire with oxygen, which is not possible by any prior art systems.
As a fire-preventive modality, the environment of normobaric breathable hypoxic air in normally occupied facilities, including railroad tunnels, entirely eliminates the possibility of ignition of all common inflammable materials. As a fire-extinguishing option the effluent discharge of breathable hypoxic air would eliminate fire of any size and origin in seconds, while simultaneously evacuating toxic combustion gases and providing people with fresh breathable air. Smoke evacuation in this way does not feed the fire with oxygen, as in the case of usual forced ventilation with fresh atmospheric air.
The system can be activated by detection and control equipment for automatic system operation along with providing local and remote manual operation as needed. The system can be engineered for preventive or suppressive mode, as well as a combination of both.
FirePASS(trademark) satisfies all critically important properties required for tunnel fire suppression, such as:
fire suppression efficiency;
reignition quenching;
electrical non-conductivity;
non-corrosivity to metals;
polymeric materials compatibility;
stability under long-term storage;
toxicity of the chemical and its combustion and decomposition products;
speed of dispersion; and
safety and occupational health requirements.
In its suppressive mode FirePASS(trademark) for tunnels requires sufficient amount of the breathable agent stored in high pressure containers. However, after initial discharge from containers, the agent continues to be produced from ambient air by hypoxic generators and delivered to the site of a fire for as long as needed. The system can be operated by the tunnel operator within established criteria or on the instruction of the Fire Services Incident Operator. A single car fire with no traffic congestion may not warrant its operation. A fully involved or developing car fire resulted from an accident or terror act and spreading to other vehicles may require its activation.
A hypoxic agent can be used also as a fire-preventive modality in the railroad and funicular tunnels. This application of FirePASS(trademark) technology can be achieved with the help of semi-airtight doors that turn the inner volume of a tunnel into an enclosure, having the atmosphere of NBHA inside. The doors will be opened automatically at the approach of train and closed again after it has passed through. The necessary amount of NBHA in the tunnel will be maintained by continuous compensatory discharge from piping.
The tunnel-specific configuration of FirePASS(trademark) provides high reliability and efficiency. The system operational reliability cannot be affected by electric power supply failure, because it relies on built-in autonomic compressors and a backup power supply. After the initial agent discharge from pressurized containers the hypoxic generators would be automatically started and will produce sufficient amount of the agent for tunnel ventilation. Due to the addressed delivery of the agent via gas delivery hose the loss of agent is minimized.
The system is also resistant to structural damage. Thus, even in the case of a major explosion in the tunnel, causing damage to the gas delivery hose and communication cables, the fire-affected area of a tunnel can be flooded and further ventilated with the breathable hypoxic agent.
An important advantage of the FirePASS(trademark) technology in comparison to all other existing fire-suppressive systems is that its fire-preventative and suppressive agent is produced at site by hypoxic air generators that consume nothing but electric energy. There are no gas transportation and refilling problems, and a low maintenance costs and simple integration in existing structural configurations are the obvious advantages of this technology.
The equipment for FirePASS(trademark) technology exists in a variety of different prototypes, and can be manufactured and installed in specified applications both for newly-planned tunnels and for retrofitting-existing ones. The system can be periodically tested and exercised, it allows quick response and permits the tunnel operator positive control in the event of a fire. Approximate cost benefit analyses shows that the cost of the system is significantly less than the expected costs of damages, liability, and loss of a vital transportation link that may result from a single catastrophic fire.
The principal objects of this invention are as follows:
A method for producing and selectively delivering a breathable fire-suppressive hypoxic composition inside a part of a tunnel or other human-occupied environment affected by fire.
A method of extinguishing an ongoing fire in a tunnel by releasing a pressurized fire-extinguishing hypoxic composition into a location where fire is detected. This rapidly replaces the contaminated normoxic atmosphere in such an environment with the human-breathable hypoxic fire-extinguishing atmosphere and suppressing any fire at once.
The provision of equipment that can produce, store and deliver the breathable hypoxic fire-extinguishing composition.
The provision of a fire suppressant delivery system consisting of an expandable gas delivery hose, fire detectors installed at intervals along the hose""s length and puncturing devices that can puncture the hose in any location where a fire is detected. This will allow the discharge of the fire suppressant from pressurized storage containers and flooding the portion of a tunnel affected by fire. Additional supply of hypoxic agent from hypoxic generators will maintain a fire-extinguishing atmosphere for as long as needed.
The provision of an inflatable tunnel-blocking device or plug that allows redirecting the fire-suppressant flow towards a direction opposite to the inflated plug.